﻿using SharpNoisePCL.Helpers;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace SharpNoisePCL.Noise
{
    public class PerlinNoise : INoiseGenerator
    {
        int[] permutation = {151, 160, 137, 91, 90, 15,
        131, 13, 201, 95, 96, 53, 194, 233, 7, 225, 140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23,
        190, 6, 148, 247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32, 57, 177, 33,
        88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175, 74, 165, 71, 134, 139, 48, 27, 166,
        77, 146, 158, 231, 83, 111, 229, 122, 60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244,
        102, 143, 54, 65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169, 200, 196,
        135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64, 52, 217, 226, 250, 124, 123,
        5, 202, 38, 147, 118, 126, 255, 82, 85, 212, 207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42,
        223, 183, 170, 213, 119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
        129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104, 218, 246, 97, 228,
        251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241, 81, 51, 145, 235, 249, 14, 239, 107,
        49, 192, 214, 31, 181, 199, 106, 157, 184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254,
        138, 236, 205, 93, 222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180
                             };
        int[] p = new int[512];
        bool start = true;

        float noise(float x, float y, float z)
        {
            if (start)
            {
                for (var i = 0; i < 256; i++) p[256 + i] = p[i] = permutation[i];
                start = false;
            }

            var X = (int)Math.Floor(x) & 255;                  // FIND UNIT CUBE THAT
            var Y = (int)Math.Floor(y) & 255;                  // CONTAINS POINT.
            var Z = (int)Math.Floor(z) & 255;
            x -= (int)Math.Floor(x);                                     // FIND RELATIVE X,Y,Z
            y -= (int)Math.Floor(y);                                     // OF POINT IN CUBE.
            z -= (int)Math.Floor(z);
            var u = fade(x);                                        // COMPUTE FADE CURVES
            var v = fade(y);                                        // FOR EACH OF X,Y,Z.
            var w = fade(z);

            var A = p[X] + Y;
            var AA = p[A] + Z;
            var AB = p[A + 1] + Z;                                  // HASH COORDINATES OF
            var B = p[X + 1] + Y;
            var BA = p[B] + Z;
            var BB = p[B + 1] + Z;                                  // THE 8 CUBE CORNERS,

            return Interpolaters.Lerp(Interpolaters.Lerp(Interpolaters.Lerp(grad(p[AA], x, y, z),      // AND ADD
                                           grad(p[BA], x - 1, y, z), u),                                           // BLENDED
                                   Interpolaters.Lerp(grad(p[AB], x, y - 1, z),                              // RESULTS
                                           grad(p[BB], x - 1, y - 1, z), u), v),                                      // FROM  8
                           Interpolaters.Lerp(Interpolaters.Lerp(grad(p[AA + 1], x, y, z - 1),            // CORNERS
                                           grad(p[BA + 1], x - 1, y, z - 1), u),                                   // OF CUBE
                                   Interpolaters.Lerp(grad(p[AB + 1], x, y - 1, z - 1), grad(p[BB + 1], x - 1, y - 1, z - 1), u), v), w);
        }

        float fade(float t) { return t * t * t * (t * (t * 6 - 15) + 10); }

        float grad(int hash, float x, float y, float z)
        {
            var h = hash & 15;                              // CONVERT LO 4 BITS OF HASH CODE
            var u = h < 8 ? x : y;                         // INTO 12 GRADIENT DIRECTIONS.
            var v = h < 4 ? y : h == 12 || h == 14 ? x : z;
            return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
        }


        public float Get1D(float x)
        {
            return noise(x, 0, 0);
        }

        public float Get2D(float x, float y)
        {
            return noise(x, y, 0);
        }

        public float Get3D(float x, float y, float z)
        {
            throw new NotImplementedException();
        }

        public float Get4D(float x, float y, float z, float t)
        {
            throw new NotImplementedException();
        }
    }
}
